The present invention relates to a radar camouflage material for reducing the radar back-scatter cross-section of a target object.
Radar camouflage materials are intended to protect a target object, e.g. an airplane, against detection by enemy radar or at least to make detection more difficult. Known and used for this purpose are, for example, lossy dielectric materials of various types. The major problem with such known camouflage materials is that the layers of dielectric materials required for effective camouflage are too thick to be suitable as a camouflage for aircraft.
European Patent No. 0,121,655.A2, corresponding to U.S. Pat. No. 4,581,284, discloses a composite fiber material in which, for example, soot or iron powder is embedded in such a manner that absorption of radar beams is possible. Since this material can be employed only wherever the manufacturing process includes structural aircraft components made of composite fiber materials, this material does not offer an actual solution for the problem of camouflaging metal parts.
The periodical "The Radio and Electronic Engineer", Volume 51, 1981, pages 209-218, describes a method in which hexagonal ferrites are used in camouflage layers. This produces a greater attenuation loss for the radar waves over a greater frequency range than is the case if only lossy dielectric materials are employed. Additionally, camouflage materials containing ferrites are usually thinner. In this case, a plurality of ferrite material layers are arranged one on top of the other to produce the appropriate attenuation bandwidth. This requires an expensive manufacturing process which primarily makes repairs of damaged aircraft parts more difficult.
European Patent No. 0,104,536.A2, corresponding to U.S. Pat. No. 4,684,952, discloses a method in which an antenna is constructed according to the so-called microstrip technology. This antenna is composed of a plurality of metal foil patches applied to a dielectric material to form an array. By interconnecting the antenna elements with lossy loads, the electromagnetic radiation incident on the array is partially absorbed. This causes the array to camouflage the covered surface.